Method of making same



Aug. 11, 1959 M. G. HARRis ETAL BRAZED LIGHTALLOY HEAT EXCHANGER AND METHOD OF MAKING SAME Filed June 18, 1957 lr wenlor M/cAae/ G. Harm's eyJ h a/ken V Attorneys United States Patent BRAZED LIGHT ALLOY HEAT EXCHANGER AND METHOD OF MAKING SAlVlE Michael G. Harris, Cumnor, and Sydney J. Walker, Botley, England, assignors to Morris Motors Limited, Oxford, England Application June 18, 1957, Serial No. 666,421

Claims priority, application Great Britain December 6, 1956 3 Claims. (Cl. 257245) This invention relates to brazed light alloy secondary surface heat-exchangers of pack construction, namely in which the matrix comprises thin-walled narrow tubes of elongated quasi-rectangular cross-section spaced apart at their flanks by interposed secondary heat-transfer surface elements of thin metal, affording a multiplicity of airways, the end zones of the tubes being held in tube-plates assembled from channel-section strips.

More specifically, the invention is concerned with an improved method of assembling the particular type of pack-construction heat-exchanger in which each tube is assembled, in situ, from a pair of flat rectangular sheets forming its sides with either solid or channel-type tubenoses interposed between the edges of the tube side sheets. The existing method of assembling this type of matrix, both for radiators and for oil coolers, is complicated and costly; one of the problems being to achieve, and to maintain, during brazing, correct location of all the separate tube-noses and tube-plate strips with the side sheets and intervening members making up the matrix. These strips have to be approximately one inch longer than the depth of the matrix, not only to allow seatings for the covers of the header tanks but also to enable corner tie rods to be passed through holes drilled in the projecting ends of all the strips, in spacing pieces (needed to fill the gaps caused by the tubes) and in casing plates enclosing the sides of the matrix. After the assembly has been brazed in a salt bath the ends of the tubeplate strips containing the tie rods are cut off, and the ends of those rods are trimmed to be flush with the faces of the casing plates. The tank covers, fittings and brackets are then applied by torch-brazing after the matrix has been preheated in a brazing oven.

The aim of the invention is to enable the particular type of pack-construction heat-exchanger mentioned above to be meanufactured in simpler fashion and more cheaply. To this end, according to the invention the tubenoses are arranged to project longitudinally at both ends of the tubes, and the projecting tube-nose portions and the adjoining end zones of the tube-plate channel strips are reciprocally shaped to effect interlocking engagement. This may conveniently be achieved by cutting the flanges of the channel-section tube-plate strips at their end zones, and bending the latter upwardly and then folding in half to form a flat-sided hook of inverted U-section; the projecting tube-nose portions being flattened to create spade-like terminations of appropriate width and capable of being fitted snugly into the corresponding hooks of the tubeplate strips.

a bnaz'ed light alloy heat-exchanger constructed in accord-' ance with the invention;

Figure 2 isa cross-sectional view of a tube assembly;

Figure 3 is a fragmentary perspective view of a tubeplate assembly;

Figures 4 and 5 are fragmentary perspective views of different tube-nose designs; and

Figure 6 is a fragmentary side elevation showing a modification of part of the arrangement illustrated in Figure 1.

Figure 1 represents one end portion of an oil cooler of brazed light alloy pack construction, the tubes 1 of which are each fitted internally with a sheet of thin metal corrugated longitudinally to serve as a tube-stiffener 2. The matrix is assembled by placing the hooked tubeplate channels 3 forming the top and bottom tube plates on a casing plate 4 alternately with the intervening tube assemblies (Fig. 2) comprising flat tube walls 5, internal stiifeners 2 and tube-noses 6. The spade-like terminations 7 at both ends of the tube-noses 6 are held in the hooks 8 (Fig. 3) of the tube-plate channels 3 forming the top and bottom tube plates, and sheets of thin metal 9, corrugated transversely to form airways, are inserted between the individual tube assemblies.

When the assembly of the matrix has been completed by adding the other casing plate (not shown), the inlet and outlet tank covers (one of which is shown at 10 in Figure l) are fitted between the hooked ends of the tube-plate channels 3 and held in place by bending down retaining lugs 11 provided on the casing plates, these also constituting the end Walls of the tanks. Any required fitments are riveted to the tanks or the casing plates; for example in the case of brackets by having tags on them and corresponding slots in the tanks or the casing plates, and in the case of shouldered fittings (as at 12 in Figure 1) by inserting the end of the fitting in a hole 13 in the tank or casing plate, as the case may be, and peening it. The completed assembly is clamped between brazing plates (not shown) and then brazed in a salt bath, washed, cleaned and tested.

Instead of the tube-noses being made of folded material, as at 6 (Figs. 2 and 3), they may be of the solid type 6A (Fig. 4) or of channel type 6B (Fig. 5).

In the example illustrated in Figure l, the spade-like terminations 7 of the tube-noses 6 lie parallel to the matrix faces. If desired, however, these terminations and, of course, the co-operating hooks 8 of the tube-plate channels 3, may be inclined to the matrix faces as indicated in Figure 6.

We claim:

1. A method of assembling in situ a brazed light alloy heat-exchanger of the tubular pack type having side sheets, tube noses and tube-plate channel strips, which comprises the steps of arranging for the tube-noses to project longitudinally at both ends of the side sheets, cutting the flanges of the tube-plate channel strips at their end zones, flattening said end zones to make their sidewalls co-planar with the bases of said channel strips, bending said end zones upwardly, and then folding said end zones in half to form a flat-sided hook of inverted U-section, and flattening the projecting tube nose portions to create spade-like terminations capable of being fitted snugly into the corresponding hooks of the tube-plate strips to effect interlocking engagement.

2. A brazed light alloy pack-construction heat-exchanger in which each tube is comprised of a pair of flat rectangular side sheets with tube-noses interposed at their ends, and the end zones of the tubes are held in tubeplates assembled from channel-section strips having hooklike end portions While the end zones of the tube-noses project from between the ends of the side sheets and terminate in spade-like projections which fit snugly into the hook-like end portions of; said tube plates.

3. A brazed light alloy pack-construction heat exchanger of the type in which each tube comprises a pair of flat rectangular side sheets with tube-noses interposed at their ends and the end zones of the tubes are held in tube-plates assembled from channel-section strips, characterized by the end zones of the tube-noses and of the tube-plate strips projecting beyond the ends of the tubes and being reciprocally shaped to effect interlocking engagement.

References Cited in the file of this patent FOREIGN PATENTS 662,281 Great Britain Dec. 5, 1951 

